Jenny I Shen

Stanford University, Stanford, California, United States

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Publications (12)50.53 Total impact

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    ABSTRACT: Although warfarin is indicated to prevent ischemic strokes in most patients with atrial fibrillation (AF), evidence supporting its use in hemodialysis patients is limited. Our aim was to examine outcomes after warfarin therapy initiation, relative to no warfarin use, following incident AF in a large cohort of hemodialysis patients who had comprehensive prescription drug coverage through Medicare Part D. Retrospective observational cohort study. Patients in the US Renal Data System undergoing maintenance hemodialysis who had AF newly diagnosed in 2007 to 2011, with Medicare Part D coverage, who had no recorded history of warfarin use. Warfarin therapy initiation, identified by a filled prescription within 30 days of the AF event. Death, ischemic stroke, hemorrhagic stroke, severe gastrointestinal bleeding, and composite outcomes. HRs estimated by applying Cox regression to an inverse probability of treatment and censoring-weighted cohort. Of 12,284 patients with newly diagnosed AF, 1,838 (15%) initiated warfarin therapy within 30 days; however, ∼70% discontinued its use within 1 year. In intention-to-treat analyses, warfarin use was marginally associated with a reduced risk of ischemic stroke (HR, 0.68; 95% CI, 0.47-0.99), but not with the other outcomes. In as-treated analyses, warfarin use was associated with reduced mortality (HR, 0.84; 95% CI, 0.73-0.97). Short observation period, limited number of nonfatal events, limited generalizability of results to more affluent patients. In hemodialysis patients with incident AF, warfarin use was marginally associated with reduced risk of ischemic stroke, and there was a signal toward reduced mortality in as-treated analyses. These results support clinical equipoise regarding the use of warfarin in hemodialysis patients and underscore the need for randomized trials to fill this evidence gap. Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
    No preview · Article · Jul 2015 · American Journal of Kidney Diseases
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    ABSTRACT: In the kidney transplant population with atrial fibrillation (AF), evidence regarding the effectiveness and safety of warfarin treatment is lacking. We used fee-for-service Medicare claims to identify kidney transplant recipients with newly diagnosed AF from the United States Renal Data System. Warfarin use within 30 days of AF diagnosis was ascertained from Medicare Part D prescription claims (2007-11) or using a validated algorithm (1997-2011). The study end points were (i) the composite of death, stroke or gastrointestinal bleed, (ii) death and (iii) death-censored graft failure. Warfarin user and non-user groups were balanced using inverse probability of treatment weighting and hazard ratios were (HRs) estimated using Cox regression. Among 718 subjects with an indication for anticoagulation, 24% initiated warfarin treatment within 30 days of AF diagnosis. Age was the only independent correlate of warfarin use [odds ratio = 1.02 per year; 95% confidence interval (95% CI) 1.01-1.04]. In the larger cohort of 6492 patients with AF, warfarin use [(23.5%) versus non-use (76.5%)] was associated with small and non-significant reductions in the composite of death, stroke or gastrointestinal bleed (HR = 0.92; 95% CI 0.83-1.02), death (HR = 0.92; 95% CI 0.82-1.02) and death-censored graft failure (HR = 0.90; 95% CI 0.76-1.08). Our study suggests the need for clinical trials of warfarin use in the kidney transplant population with AF.
    No preview · Article · Oct 2014 · Nephrology Dialysis Transplantation
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    ABSTRACT: Background: Heparin is commonly given during hemodialysis (HD). Patients undergoing HD have a high rate of gastrointestinal bleeding (GIB). It is unclear whether or when it is safe to give heparin after acute GIB. We describe the patterns and safety of heparin use with outpatient HD following an acute GIB. Methods: We identified patients aged ≥ 67 who, from 2004-2008, experienced GIB requiring hospitalization within 2 days of receiving maintenance HD with heparin. We used Cox regression to estimate the risk of recurrent GIB and death associated with receiving heparin the day they resumed outpatient HD post-GIB. Results: Of the 1,342 patients who had GIB, 1,158 (86%) received heparin at a median dose of 4,000 units with their first outpatient HD session after discharge from GIB. On average, their post-GIB doses were slightly lower than their pre-GIB doses (mean change: -214 ± 3,266 units, p < 0.02). However, only 27% of patients had a decrease in their dose, while 21% had their dose increased. We did not find an increased risk of death or recurrent GIB associated with using heparin post-GIB (HR; 95% confidence interval (CI), for death: 1.01; 0.69-1.48; for recurrent GIB: 0.78; 0.39-1.57). Conclusions: The vast majority of these high-risk patients received heparin on the very first day they resumed outpatient HD post-GIB, and the majority at unchanged doses to those received pre-GIB. Even if the practice was not associated with increased risks of death or re-bleeding, it highlights an area for possible system-based improvement to the care for patients on HD.
    No preview · Article · Oct 2014 · American Journal of Nephrology
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    ABSTRACT: Background-Coronary stenting in patients on dialysis has increased by nearly 50% over the past decade, despite heightened risks of associated stent thrombosis and bleeding relative to the general population. We examined clopidogrel, prasugrel or ticlopidine use after percutaneous coronary intervention (PCI) with stenting in patients on dialysis. We conducted 3-, 6-, and 12-month landmark analyses to test the hypothesis that thienopyridine discontinuation prior to those time points would be associated with higher risks of death, myocardial infarction, or repeat revascularization, and a lower risk of major bleeding episodes compared with continued thienopyridine use. Methods and Results-Using the US Renal Data System, we identified 8458 patients on dialysis with Medicare Parts A+B+D undergoing PCI with stenting between July 2007 and December 2010. Ninety-nine percent of all thienopyridine prescriptions were for clopidogrel. At 3 months, 82% of patients who received drug-eluting stents (DES) had evidence of thienopyridine use. These proportions fell to 62% and 40% at 6 and 12 months, respectively. In patients who received a bare-metal stent (BMS), 70%, 34%, and 26% of patients had evidence of thienopyridine use at 3, 6, and 12 months, respectively. In patientswho received a DES, there was a suggestion of higher risks of death or myocardial infarction associated with thienopyridine discontinuation in the 3-, 6-, and 12-months landmark analyses, but no higher risk of major bleeding episodes. In patients who received a BMS, there were no differences in death or cardiovascular events, and possibly lower risk of major bleeding with thienopyridine discontinuation in the 3-and 6-month landmark analyses. Conclusions-The majority of patients on dialysis who undergo PCI discontinue thienopyridines before 1 year regardless of stent type. While not definitive, these data suggest that longer-term thienopyridine use may be of benefit to patients on dialysis who undergo PCI with DES.
    Preview · Article · Oct 2014 · Journal of the American Heart Association

  • No preview · Article · May 2014 · American Journal of Kidney Diseases
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    ABSTRACT: Heparin is commonly used to anticoagulate the hemodialysis (HD) circuit. Despite the bleeding risk, no American standards exist for its administration. We identified correlates and quantified sources of variance in heparin dosing for HD. We performed a cross-sectional study of patients aged 67 years or older who underwent HD with heparin on one of two randomly chosen days in 2008 at a national chain of dialysis facilities. Using a mixed effects model with random intercept for facility and fixed patient and facility characteristics, we examined heparin dosing at patient and facility levels. The median heparin dose among the 17 722 patients treated in 1366 facilities was 4000 (25th-75th percentile: 2625-6000) units. In multivariable-adjusted analyses, higher weight, longer session duration, catheter use, and dialyzer reuse were significantly associated with higher heparin dose. Dose also varied considerably among census divisions. Of the overall variance in dose, 21% was due to between-facility differences, independent of facilities' case mix, geography, size, or rurality; 79% was due to differences at the patient level. The patient and facility characteristics in our model explained only 25% of the variance at the patient level. Despite the lack of standards for heparin administration, we noted patterns of use, including weight-based and time-dependent dosing. Most of the variance was at the patient level; however, only a quarter of it could be explained. The high amount of unexplained variance suggests that factors other than clinical need are driving heparin dosing and that there is likely room for more judicious dosing of heparin. Copyright © 2014 John Wiley & Sons, Ltd.
    No preview · Article · May 2014 · Pharmacoepidemiology and Drug Safety

  • No preview · Article · Jan 2014 · American Journal of Kidney Diseases
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    ABSTRACT: Background Although heparin is used to anticoagulate the extracorporeal circuit for most patients on maintenance hemodialysis (HD), some patients undergo heparin-free HD. We describe the determinants of heparin-free HD and its association with adverse outcomes using data from a national dialysis provider merged with Medicare claims.Methods We identified patients aged ≥67 years with no recent history of warfarin use who initiated maintenance HD from 2007 to 2008. We applied the Cox regression to a propensity score-matched cohort to estimate the hazards of all-cause mortality, bleeding (gastrointestinal hemorrhage, hemorrhagic stroke, other hemorrhage), atherothrombosis (ischemic stroke, myocardial infarction) and venous thromboembolism (VTE) (deep vein thrombosis, pulmonary embolism).ResultsAmong 12 468 patients, 836 (6.7%) were dialyzed heparin-free. In multivariable-adjusted analyses, a history of gastrointestinal bleeding, hemorrhagic stroke and lower hemoglobin and platelet counts were associated with higher odds of heparin-free HD. Heparin-free HD use also varied as much as 4-fold by facility region. We found no significant association of heparin-free HD with all-cause mortality [hazard ratio (HR) 1.08; 95% confidence interval (CI): 0.94-1.26], bleeding (HR 1.15; 95% CI: 0.83-1.60), atherothrombosis (HR 1.09, 95% CI: 0.90-1.31) or VTE (HR 1.23, 95% CI: 0.93-1.64) compared with HD with heparin.Conclusions Patient markers of increased risk of bleeding and facility region associated with heparin-free HD use. Despite the potential benefits of avoiding heparin use, heparin-free HD was not significantly associated with decreased hazards of death, bleeding or thrombosis, suggesting that it may be no safer than HD with heparin.
    No preview · Article · Apr 2013 · Nephrology Dialysis Transplantation
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    ABSTRACT: Atrial fibrillation is common among patients with end-stage renal disease undergoing hemodialysis. Although oral anticoagulation is recommended for stroke prevention in most patients with atrial fibrillation, limited evidence is available to guide treatment in hemodialysis patients with this arrhythmia. We summarize the available evidence on the epidemiology of atrial fibrillation in dialysis patients and review the data on the effectiveness of oral anticoagulation in this population. Atrial fibrillation is increasingly common in patients undergoing chronic hemodialysis, especially among older patients wherein one in six patients is diagnosed with this arrhythmia. Patients with atrial fibrillation experience double the mortality of otherwise similar patients without it. Few hemodialysis patients with atrial fibrillation receive oral anticoagulation, which is consistently associated with excess risks of hemorrhagic stroke. Observational studies did not detect a beneficial association of oral anticoagulation with the risk of ischemic stroke, with some studies describing higher risks of ischemic stroke among warfarin users. New therapeutic options including one oral direct thrombin inhibitor and two oral factor Xa inhibitors have become available, but were not tested in patients with advanced kidney disease. Atrial fibrillation is increasingly common in patients undergoing hemodialysis, yet little is known about the optimal management of these patients. The current evidence does not support net benefits from oral anticoagulation in the dialysis population.
    No preview · Article · Nov 2012 · Current opinion in nephrology and hypertension
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    ABSTRACT: Objectives: Switching from peritoneal dialysis (PD) to hemodialysis (HD) is undesirable, because of complications from temporary vascular access, disruption of daily routine, and higher costs. Little is known about the role that social factors play in technique failure. Design, setting, participants, measurements: We followed for 3 years a nationally representative cohort of US patients who initiated PD in 1996 - 1997. Technique failure was defined as any switch from PD to HD for 30 days or more. We used Cox regression to examine associations between technique failure and demographic, medical, social, and pre-dialysis factors. We estimated hazard ratios (HRs) with 95% confidence intervals (CIs). Results: We identified an inception cohort of 1587 patients undergoing PD. In multivariate analysis, female sex (HR: 0.78; 95% CI: 0.64 to 0.95) was associated with lower rates of technique failure, and black race [compared with white race (HR: 1.48; 95% CI: 1.20 to 1.82)] and receiving Medicaid (HR: 1.48; 95% CI: 1.17 to 1.86) were associated with higher rates. Compared with patients who worked full-time, those who were retired (HR: 1.49; 95% CI: 1.07 to 2.08) or disabled (HR: 1.38; 95% CI: 1.01 to 1.88) had higher rates of failure. Patients with a systolic blood pressure of 140 - 160 mmHg had a higher rate of failure than did those with a pressure of 120 - 140 mmHg (HR: 1.24; 95% CI: 1.00 to 1.52). Earlier referral to a nephrologist (>3 months before dialysis initiation) and the primary decision-maker for the dialysis modality (physician vs patient vs shared) were not associated with technique failure. Conclusions: This study confirms that several socio-demographic factors are associated with technique failure, emphasizing the potential importance of social and financial support in maintaining PD.
    Preview · Article · Oct 2012
  • Jenny I Shen · Wolfgang C Winkelmayer
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    ABSTRACT: Anticoagulation is essential to hemodialysis, and unfractionated heparin (UFH) is the most commonly used anticoagulant in the United States. However, there is no universally accepted standard for its administration in long-term hemodialysis. Dosage schedules vary and include weight-based protocols and low-dose protocols for those at high risk of bleeding, as well as regional anticoagulation with heparin and heparin-coated dialyzers. Adjustments are based largely on clinical signs of under- and overanticoagulation. Risks of UFH use include bleeding, heparin-induced thrombocytopenia, hypertriglyceridemia, anaphylaxis, and possibly bone mineral disease, hyperkalemia, and catheter-associated sepsis. Alternative anticoagulants include low-molecular-weight heparin, direct thrombin inhibitors, heparinoids, and citrate. Anticoagulant-free hemodialysis and peritoneal dialysis also are potential substitutes. However, some of these alternative treatments are not as available as or are more costly than UFH, are dependent on country and health care system, and present dosing challenges. When properly monitored, UFH is a relatively safe and economical choice for anticoagulation in long-term hemodialysis for most patients.
    No preview · Article · May 2012 · American Journal of Kidney Diseases

  • No preview · Conference Paper · Apr 2012